Vehicle Seat

ABSTRACT

Provided is a vehicle seat having a seat back that can be folded forward, in which the buckle is prevented from interfering with the seat hack when the seat back is folded forward. A seat cushion frame (F 1 ) rotatably attached to the seat back frame (F 2 ) includes a pair of side frames ( 11 ) extending in a fore and aft direction, a front frame ( 12 ) extending between front parts of the side frames, and a rear frame ( 13 ) extending between rear parts of the side frames and provided with a curved portion ( 13 A) protruding forward in a middle part thereof. A buckle support arm is located behind the curved portion, the curved portion being dimensioned so as not to interfere with the buckle when the buckle support arm is in a stowed position.

TECHNICAL FIELD

The present invention relates to a vehicle seat configured to be mournedto a vehicle or the like.

BACKGROUND ART

In a rear seat of a vehicle having a seat cushion configured to seat twopassengers, a buckle that can be coupled with a tongue plate of a seatbelt is required to be provided in a rear central part of the seatcushion. In such a rear seat, it is known to provide a recess in alaterally extending frame portion positioned behind the seat cushion bycurving a central part of the laterally extending frame portion in aforward direction, form a notch in a central part of the rear edge ofthe seat cushion, and provide an arm connecting a buckle to the floor ofthe vehicle to extend through the recess and the notch so that thebuckle that is passed through the notch is located and exposed above theseat surface of the seat cushion. See Patent Document 1, for instance.

PRIOR ART DOCUMENT(S) Patent Document(s)

Patent Document 1: JP3070393B

SUMMARY OF THE INVENTION Task to be Accomplished by the Invention

However, the vehicle seat disclosed in Patent Document 1 is configuredin such a manner that the buckle is always maintained above the seatsurface of the seat cushion so the buckle prevents the seat back frombeing folded forward.

In view of such a problem of the prior art, a primary object of thepresent invention is to provide a vehicle seat having a seat back thatcan be folded forward, and prevent the buckle from interfering with theseat back when folding the seat back forward.

To achieve such an object, one embodiment of the present inventionprovides a vehicle seat, comprising: a seat back frame (F2) attached toa floor (FL) so as to be rotatable in a fore and aft direction within aprescribed range; a seat cushion frame (F1) rotatably attached to theseat back frame, and configured to move forward when the seat back frameis tilted forward; and a buckle support arm (44) having a base endattached to the floor so as to be rotatable in the fore and aftdirection, and a free end fitted with a buckle (45) configured to becoupled with a tongue plate of a seat belt, the buckle support arm beingrotatable between a use position where the buckle is positioned abovethe base end of the buckle support arm, and a stowed position where thebuckle is positioned more forward than in the use position; wherein theseat cushion frame includes a pair of side frames located on either sideand extending in the fore and aft direction, a front frame (12)extending between front parts of the side frames, and a rear frame (13)extending between rear parts of the side frames and provided with acurved portion (13A) protruding forward in a laterally middle partthereof, and wherein the buckle support arm is located behind the curvedportion, the curved portion being dimensioned so as not to interferewith the buckle when the buckle support arm is in the stowed position.

Since the curved portion is dimensioned so as not to interfere with thebuckle when the buckle support arm is in the stowed position, the bucklesupport arm can be positioned in the stowed position such that thebuckle does not interfere with the seat back when the seat back isfolded forward.

Preferably, in this embodiment, the curved portion is positioned in arotational locus of the buckle support arm and the buckle when the seatcushion frame is positioned in a rearmost position in correspondence toa position of the seat back frame, and out of the rotational locus ofthe buckle support arm and the buckle when the seat cushion frame ispositioned in a more forward position in correspondence to the positionof the seat hack frame.

As the seat back frame rotates forward and the seat cushion frame movesforward, the buckle support arm moves to the stowed position. Inparticular, as the seat back tilts forward, the buckle support arm movesto the stowed position so that an interference between the buckle andthe seat back can be avoided.

According to a preferred embodiment of the present invention, thevehicle seat further comprises a seat cushion pad (34) supported by theseat cushion frame, and provided with a recessed portion (34A) recessedforward from a part of a rear edge of the seat cushion framecorresponding to the curved portion, and the buckle support arm ispositioned in the recessed portion in such a manner that the seatcushion pad is positioned in the rotational locus of the buckle supportarm and the buckle when the seat cushion frame is positioned in therearmost position in correspondence to the position of the seat backframe, and out of the rotational locus of the buckle support arm and thebuckle when the seat cushion frame is positioned in a more forwardposition in correspondence to the position of the seat back frame.

Thereby, the size of the recessed portion of the seat cushion pad can beminimized so that the seat surface area of the seat cushion can bemaximized.

Preferably, in any of the foregoing embodiments, an upper end of thebuckle is lower than an upper surface of the seat cushion pad in thestowed position.

Thereby, when the seat back is folded forward, the buckle in the stowedposition is prevented from interfering with the seat back.

Preferably, in any of the foregoing embodiments, the vehicle seatfurther comprises a biasing device (47) for urging the buckle supportarm toward the use position.

Thereby, when the vehicle seat is in the use position, the bucklesupport arm is urged toward the use position by the biasing device.

Preferably, in any of the foregoing embodiments, the vehicle seatfurther comprises a reinforcing member (16) extending in the fore andaft direction between the curved portion and the front frame.

Thereby, the stiffness of the seat cushion frame is maintained even whenthe rear frame is provided with the curved portion.

Preferably, in any of the foregoing embodiments, the vehicle seatfurther comprises an intermediate frame (14) extending laterally betweenthe side frames intermediately between the front frame and the rearframe, and a reinforcing member (16) extending in the fore and aftdirection between the curved portion and the intermediate frame.

According to this arrangement, the intermediate frame effectivelyincreases the stiffness of the seat cushion frame. Even though the rearframe is provided with the curved portion, the stiffness of the seatcushion frame is maintained by the reinforcing member.

Preferably, in any of the foregoing embodiments, the rear frame includesa left portion (13B) and a right portion (13C) extending laterally oneither side of the curved portion, and the seat cushion frame defines apair of seating parts, the left portion forming a rear part of one ofthe seating parts, the right portion forming a rear part of the other ofthe seating parts, and the curved portion is positioned at a boundarybetween the two seating parts.

Since the curved portion is positioned away from the buttocks of theoccupants of the two seating parts of the seat configured to seat twooccupants, the occupants are prevented from experiencing any discomfortwhich could be otherwise caused by the curved portion.

Preferably, in any of the foregoing embodiments, the curved portion, theleft portion, and the right portion are formed by a continuous pipemember.

Thereby, the rear frame has a simple structure.

Preferably, in any of the foregoing embodiments, the left portion andthe right portion are vertically offset from each other.

Thereby, the thickness of the seat cushion pad for a part of the seatcushion located in a part of the rear frame which is downwardly offsetcan be increased.

Preferably, in any of the foregoing embodiments, the seat cushion frameforms two seating parts in a rear seating arrangement including a leftseating part (31), a middle seating part (32), and a right seating part(3) that are arranged laterally, the two seating parts being formed byone of the left and right seating parts, and the middle seating part,and one of the left portion and the right portion corresponding to theleft seating part or the right seating part is offset downward relativeto the other of the left portion and the right portion corresponding tothe middle seating part.

Thereby, the thickness of the seat cushion pad in the left seating partor the right seating part, which is used more frequently than the middleseating part can be given with an increased thickness.

Preferably, in any of the foregoing embodiments, the vehicle seatfurther comprises a rear frame reinforcing member (15) connected to theleft portion and the right portion, and curved and/or bent downward in apart thereof corresponding to the curved portion.

Thereby, the rear frame can be reinforced without interfering with thebuckle support arm.

Preferably, in any of the foregoing embodiments, the curved portion hasa V shaped configuration projecting forward in plan view.

Thereby the structure of the rear frame is simplified and manufacturingthereof is facilitated.

Effect of the Invention

According to the above structure, in the vehicle seat having the seatback that can be tilted forward, the buckle can be prevented frominterfering with the seat back when the seat back is tilted forward.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 is a perspective view of a vehicle seat according to a firstembodiment of the present invention;

FIG. 2 is a perspective view of a frame of the vehicle seat according tothe first embodiment;

FIG. 3 is a plan view of a seat cushion frame;

FIG. 4 is a rear view of a seat cushion frame;

FIG. 5 is a sectional view of the vehicle seat in a use state(corresponding to a cross sectional view taken along line A-A of FIG.1);

FIG. 6 is a sectional view showing the vehicle seat in an intermediatestate between the use state and a folded state (corresponding to a crosssectional view taken along line A-A of FIG. 1);

FIG. 7 is a sectional view showing the vehicle seat in the folded state(corresponding to a cross sectional view taken along line A-A of FIG.1);

FIG. 8 is a sectional perspective view of a buckle support arm(corresponding to a cross sectional view taken along line A-A of FIG.1);

FIG. 9 is a plan view showing a seat cushion frame according to a secondembodiment of the present invention; and

FIG. 10 is a rear view showing a seat cushion frame according to a thirdembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A vehicle rear seat configured as an automotive rear seat (including asecond row seat and a third row seat) according to an embodiment of thepresent invention is described in the following with reference to theappended drawings. The direction as used in the following description isbased on the view point of an occupant seated in the vehicle seat.

First Embodiment

As shown in FIG. 1 and FIG. 2, a vehicle seat S includes a seat cushionS1 including a seat cushion frame F1, and a seat hack S2 including aseat hack frame F2. The lower end of the seat back frame F2 is attachedto the rear end of the seat cushion frame F1 so as to be rotatable inthe fore and aft direction via a pair of rear links 1. The front end ofthe seat cushion frame F1 is supported by a pair of front brackets 3provided on the floor FL via a pair of right and left front links 2,respectively. Each of the front links 2 is supported by thecorresponding front bracket 3 so as to be rotatable in the fore and aftdirection about an axial line extending laterally, and is rotatablyconnected to the scat cushion frame F1 about an axial line extendinglaterally above the earlier said axial line. A lower part of the seatback frame F2 is supported by the rear bracket 4 provided on the floorFL so as to be rotatable in the fore and aft direction about a supportaxial line 4A extending laterally (see FIG. 5).

By placing a seat cushion pad 34 and a skin member on the seat cushionframe F1, the seat cushion S1 is formed. By attaching the seat back pad35 and a skin member on the seat back frame F2, the seat back S2 isformed. The seat cushion frame F1 and the seat back frame F2 may beformed by combining metallic members such as metal plate members, pipemembers and rod members.

As shown in FIG. 3, the seat cushion frame F1 includes a pair of leftand right side frames 11 extending in the fore and aft direction, afront frame 12 extending between the front parts of the left and rightside frames 11, and a rear frame 13 extending between rear parts of theleft and right side frames 11 so as be formed into a rectangular frameshape. The right and left front links 2 are rotatably connected to thefront frame 12. The seat cushion frame F1 is further provided with anintermediate frame 14 extending laterally between the left and rightside frames intermediately between the front frame 12 and the rear frame13. The left and right side frames 11 and the front frame 12 are formedby bending a pipe member having a circular cross section. Theintermediate frame 14 is formed of a pipe member having a circular crosssection.

The rear frame 13 is provided with a curved portion 13A that is bentand/or so as to protrude forward in a laterally intermediate partthereof. Further, the rear frame 13 is provided with a left portion 13Band a right portion 13C extending laterally on either side of the curvedportion 13A.

The left portion 13B and the right portion 13C are linearly formed. Theleft end of the left portion 13B is connected to the left side frame 11,and the right end of the right portion 13C is connected to the rightside frame 11. As shown in FIG. 4, the left portion 13B and the rightportion 13C are vertically offset from each other and in parallel toeach other so that the right portion 13C is located higher than the leftportion 13B. In the present embodiment, the right side frame 11 isdisposed no higher than the left side frame 11 so that the left end partof the left portion 13B is bent upward to be connected to the left sideframe 11.

The curved portion 13A is formed in a V shape protruding forward in planview. The left end of the curved portion 13A is connected to the rightend of the left portion 13B, and the right end of the curved portion 13Ais connected to the left end of the right portion 13C. As shown in FIG.4, the curved portion 13A is inclined vertically so as to getprogressively higher from the left end to the right end.

The curved portion 13A, the left portion 13B, and the right portion 13Care formed by a single continuous pipe member having a circular crosssection, and the curved portion 13A is formed by bending the pipemember. Further, the rear frame 13 is formed of a pipe member having asmaller diameter than the pipe member forming the side frame 11, thefront frame 12, and the intermediate frame 14. Further, the rear frame13 is disposed lower than the front frame 12 and the intermediate frame14 so as to define a seat surface inclined downward toward the rear soas to get progressively lower from the front end to the rear end.

As shown in FIG. 4, to the rear frame 13 is attached a rear framereinforcing member 15 extending laterally, and having a left endconnected to the left portion 13B and a right end connected to the rightportion 13C. The rear frame reinforcing member 15 is shaped in such amanner that a central part 15A thereof corresponding to the curvedportion 13A is bent and/or curved downward in a rectangular shape. Therear frame reinforcing member 15 is formed by bending a metal rod, andis joined to the left portion 13B and the right portion 13C of the rearframe 13 by welding.

As shown in FIG. 3, a reinforcing member 16 extends linearly in the foreand aft direction between the curved portion 13A and the intermediateframe 14. The reinforcing member 16 has a front end connected to theintermediate frame 14 and a rear end connected to the curved portion13A. The reinforcing member 16 is formed of a metal rod, and is joinedto the intermediate frame 14 and the curved portion 13A by welding.

A plurality of S-shaped springs 17 extend in the fore and aft directionbetween the left portion 13B and the intermediate frame 14, and betweenthe right portion 13C and the intermediate frame 14. The S-shapedsprings 17 are each bent laterally in a wavy shape, and jointly supportthe seat cushion pad 34 forming the seat cushion S1 from below.

The seat back frame F2 includes a pair of left and right side frames 21extending vertically, an upper frame 22 extending between the upperparts of the left and right side frames 21, and a lower frame 23positioned below the lower ends of the left and right side frames 21,and extending laterally in parallel with the upper frame 22 so as toform a substantially rectangular frame shape. The seat back frame F2further includes an intermediate frame 24 extending vertically betweenthe upper frame 22 and the lower frame 23 intermediately between theleft and right side frames 21. The left and right side frames 21 and theupper frame 22 are formed by bending a single pipe member having acircular cross section. The lower frame 23 and the intermediate frame 24are each formed by a pipe member having a circular cross section. A flatplate-shaped pan frame 25 is attached to the rear sides of the sideframe 21, the upper frame 22, the lower frame 23, and the intermediateframe 24.

The seat back frame F2 is rotatably connected to the rear brackets 4 atthe lower ends of the left and right side frames 21. The rear ends ofthe left and right rear links 1 are connected to the lower parts of theleft and right side frames 21 of the seat back frame F2, respectively,so as to be rotatable around an axial line extending laterally. Further,the front ends of the left and right rear links 1 are connected to therear parts of the side frames 11 of the left and right seat cushionframes F1, respectively, so as to be rotatable around an axial lineextending laterally.

As shown in FIG. 1, in a rear seating arrangement of a vehicle having aleft seating part 31, a middle seating part 32 and a right seating part33 arranged laterally in a single row, the vehicle seat S according tothe present embodiment provides the left seating part 31 and the middleseating part 32. In other words, the seat cushion frame F1 forms thebottom support for the left seating part 31 and the middle seating part32, and the scat back frame F2 forms the back support for the leftseating part 31 and the middle seating part 32. The right seating part33 is formed by a separate vehicle seat provided separately from thevehicle seat forming the left seating part 31 and the middle seatingpart 32.

The seat cushion S1 of the left seating part 31 and the middle seatingpart 32 is formed by the seat cushion pad 34, and the seat back S2 ofthe left seating part 31 and the middle seating part 32 is formed by theseat back pad 35. A laterally middle part of a rear edge of the seatcushion pad 34 is provided with a recessed portion 34A which is recessedforward from the rear edge. The recessed portion 34A is formed in a partcorresponding to the curved portion 13A of the rear frame 13. In otherwords, the rear edge of the seat cushion pad 34 is formed so as toconform to the shape of the rear flame 13. Thus, a recess 36 is formedin a laterally middle part of the seat cushion S1 owing to the curvedportion 13A of the rear frame 13 and the recessed portion 34A of theseat cushion pad 34. Further, the right end of the rear part of the seatcushion S1 is provided with a recess 37 which is recessed forward fromthe rear edge of the seat cushion S1.

In the rear frame 13 of the seat cushion frame F1, the left portion 13Bforms a rear part of the left seating part 31, the right portion 13Cforms a rear part of the middle seating part 32, and the curved portion13A is located on the boundary between the left seating part 31 and themiddle seating part 32. As shown in FIG. 4, the left portion 13B isdisposed downward with respect to the right portion 13C, and the part ofthe seat cushion pad 34 located on the left portion 13B is thicker thanthe part thereof located on the middle seating part 32. Therefore, thesitting comfort of the left seating part 31 which is expected to be morefrequently used than the middle seating part 32 can be improved. Inaddition, since the curved portion 13A is positioned away from a partcorresponding to the lower side of the buttocks of the seat occupant,the seat occupant is prevented from experiencing any discomfort owing tothe presence of the curved portion 13A.

The back side of the seat back S2 is provided with a latch 5 fordetachably engaging a striker (not shown) provided on a side panelforming the side wall of the passenger compartment of the vehicle. Byengaging the latch 5 with the striker, the seat back S2 is maintained inthe upright position. At this time, the seat cushion S1 connected to theseat back S2 by the left and right rear links 1 is in a predeterminedseating position suitable for seating corresponding to the uprightposition of the seat back S2. This state is referred to as the use stateof the vehicle seat S. When the engagement between the latch 5 and thestriker is released, the seat back S2 can be rotated in the forwarddirection. As the seat back S2 rotates forward, the seat cushion S1coupled to the seat back S2 by the left and right rear links 1 movesforward and downward (see FIG. 6). The state in which the seat back S2is folded forward so as to overlap with the upper surface of the seatcushion S1 is referred to as the folded state of the vehicle seat (seeFIG. 7).

An upper part or at least a part of a buckle device 41 for the seat beltof the left seating part 31 is disposed in the recess 36 of the seatcushion S1. More specifically, the upper part of the buckle device 41 ispassed through the inside of the curved portion 13A of the rear frame 13and is disposed inside the recessed portion 34A of the seat cushion pad34. The seat belt buckle device 42 of the middle seating part 32 and theseat belt buckle device 43 of the right seating part 33 are disposed inthe recess 37 of the seat cushion S1.

As shown in FIG. 8, the bugle device 41 includes a buckle support arm 44and a buckle 45 fixedly secured to the free end of the buckle supportarm 44. The buckle 45 is configured to detachably engage a tongue plateof the seat belt. The base end of the buckle support arm 44 is supportedby a bracket 46 which is fixedly secured to the floor FL so as to berotatable in the fore and aft direction. As a result, the buckle supportarm 44 can be rotated in the fore and aft direction between a useposition where the buckle 45 is positioned above the base end of thebuckle support arm 44, and a stowed position where the buckle 45 ispositioned forward with respect to the use position. A biasing device 47is provided between the bracket 46 and the buckle support arm 44. Thebiasing device 47 may include a torsion coil spring, for instance, thaturges the buckle support arm 44 toward the use position with respect tothe bracket 46.

The buckle support arm 44 is disposed in the recess 36 of the seatcushion S1. More specifically, the buckle support arm 44 passes throughthe inside of the curved portion 13A of the rear frame 13, and isdisposed inside the recessed portion 34A of the seat cushion pad 34.

When the vehicle seat S is in the use state, the buckle support arm 44is urged by the biasing device 47 to be in the use position, and atleast a part of the buckle 45 is located above the upper surface of theseat cushion S1 (the seat cushion pad 34) (See FIG. 5). At this time,the buckle 45 is located in front of the lower end part of the seat backS2 and is disposed in a space defined by the recess 36 and the frontsurface of the seat back S2. When the vehicle seat S is in the usestate, the curved portion 13A of the rear frame 13 and the seat cushionpad 34 are positioned within the rotational locus of the buckle device41 including the buckle 45 and the buckle support arm 44 so that thebuckle support arm 44 cannot be moved to the stowed position. When thevehicle seat S is in the folded state, the seat cushion S1 has movedforward from the position corresponding to the use state of the vehicleseat S. Therefore, the curved portion 13A of the rear frame 13 and theseat cushion pad 34 are not positioned in the rotational locus of thebuckle device 41 including the buckle 45 and the buckle support arm 44so that the buckle support arm 44 can move to the stowed position. Whenthe buckle support arm 44 is in the stowed position, the buckle 45 is ina forwardly inclined state, and the upper end thereof is positionedbelow the upper surface of the seat cushion S1 (seat cushion pad 34)(see FIG. 7).

When moving the vehicle seat S from the use state to the folded state,firstly, the engagement between the striker (not shown) and the latch 5is released, and the upper side of the seat back S2 is pushed forward asshown in FIG. 6. As the seat back S2 rotates forward, the seat cushionS1 connected to the seat back S2 by the rear links 1 moves forward anddownward with respect to the floor FL.

When moving the vehicle seat S from the use state to the folded state,the curved portion 13A of the rear frame 13 and the seat cushion pad 34are displaced away from the rotational locus of the buckle device 41 asthe seat cushion S1 moves forward so that the buckle support arm 44becomes rotatable. Then, the buckle support arm 44 is pushed by the seatback S2 and rotates from the use position to the stowed position againstthe biasing force of the biasing device 47. As a result, the buckle 45changes from the upright state (FIG. 5) to the forwardly tilted state(FIG. 7). As shown in FIG. 7, when the buckle 45 is in the forwardlytilted state, the upper end thereof is positioned lower than the uppersurface of the seat cushion pad 34 so that the buckle 45 does not hinderthe rotation of the seat back S2. Therefore, the curved portion 13A andthe recessed portion 34A (36) are dimensioned so as to avoidinterference with the buckle 45 when the vehicle seat S is in the foldedstate and the buckle support arm 44 is in the stowed position.

Further, since the buckle support arm 44 can take the stowed positiononly when the seat cushion S1 has moved forward, the recessed portion34A formed in the seat cushion pad 34 can be made small so that the seatsurface area of the seat cushion S1 is maximized. Further, the necessarybend of the curved portion 13A of the rear frame 13 can be minimized.

In addition, since the reinforcing member 16 extends between the curvedportion 13A of the rear frame 13 of the seat cushion frame F1 and theintermediate frame 14, even though the rear frame 13 is provided withthe curved portion 13A, the stiffness of the rear frame 13 can beensured. In addition, since the rear frame reinforcing member 15 isconnected to the rear frame 13, the rear frame 13 can be reinforcedwithout interfering with the buckle support arm 44.

Second Embodiment

A vehicle seat S according to a second embodiment of the presentinvention is described in the following. The reinforcing member 16extended between the curved portion 13A and the intermediate frame 14 inthe first embodiment, but may also extend between the curved portion 13Aand the front frame 12 as shown in FIG. 9. This arrangement providessimilar advantages to those of the first embodiment where thereinforcing member 16 extends between the curved portion 13A and theintermediate frame 14. More specifically, the stiffness of the seatcushion frame F1 by virtue of the intermediate frame 14. Even when therear frame 13 is provided with the curved portion 13A, the reinforcingmember 16 is effective in ensuring the stiffness of the seat cushionframe F1.

Third Embodiment

A vehicle seat S according to a third embodiment of the presentinvention is described in the following. In the first embodiment, theright portion 13C was arranged at a position higher than the leftportion 13B, hut as shown in FIG. 10, the left portion 13B and the rightportion 13C may also be arranged at the same height while a bracket 18is provided on the upper face of the right portion 13C so that the uppersurface of the right portion 13C is in effect higher than the uppersurface of the left portion 13B. This arrangement also providesadvantages similar to those of the above mentioned arrangement where theright portion 13C is positioned higher than the left portion 13B. Morespecifically, the thickness of the seat cushion pad 34 in the leftseating part 31 can be increased in view of the fact that the leftseating part 31 is likely to be more frequently used than the middleseating part 32.

Although the present invention has been described in terms of specificembodiments, the present invention is not limited by such embodiments,but can be modified and substituted without departing from the spirit ofthe present invention. For example, in the above described embodiments,the buckle support arm 44 was configured to be rotatable to the stowedposition only when the seat cushion S1 has moved forward. However, in analternate embodiment, the vehicle seat S is configured or dimensioned soas to avoid interfering with the buckle even when the buckle support arm44 is in the stowed position. Thereby, the buckle support arm 44 can berotated to the stowed position even when the vehicle seat S is in theuse state.

GLOSSARY OF TERMS

-   11: side frame-   12: front frame-   13: rear frame-   13A: curved portion-   13B: left portion-   13C: right portion-   14: intermediate frame-   15: rear frame reinforcing member-   16: reinforcing member-   31: left seating part-   32: middle seating part-   33: right seating part-   34: seat cushion pad-   34A: recessed portion-   36: recess-   41: buckle device-   44: buckle support arm-   45: buckle-   47: biasing device-   FL: floor-   F1: seat cushion frame-   F2: seat back frame-   S: vehicle seat-   S1: seat cushion-   S2: seat back

1. A vehicle seat, comprising: a seat back frame attached to a floor soas to be rotatable in a fore and aft direction within a prescribedrange; a seat cushion frame rotatably attached to the seat back frame,and configured to move forward when the seat hack frame is tiltedforward; and a buckle support arm having a base end attached to thefloor so as to be rotatable in the fore and aft direction, and a freeend fitted with a buckle configured to be coupled with a tongue plate ofa seat belt, the buckle support arm being rotatable between a useposition where the buckle is positioned above the base end of the bucklesupport arm, and a stowed position where the buckle is positioned moreforward than in the use position; wherein the seat cushion frameincludes a pair of side frames located on either side and extending inthe fore and aft direction, a front frame extending between front partsof the side frames, and a rear frame extending between rear parts of theside frames and provided with a curved portion protruding forward in alaterally middle part thereof, and wherein the buckle support arm islocated behind the curved portion, the curved portion being dimensionedso as not to interfere with the buckle when the buckle support arm is inthe stowed position.
 2. The vehicle seat according to claim 1, whereinthe curved portion is positioned in a rotational locus of the bucklesupport arm and the buckle when the seat cushion frame is positioned ina rearmost position in correspondence to a position of the seat backframe, and out of the rotational locus of the buckle support arm and thebuckle when the seat cushion frame is positioned in a more forwardposition in correspondence to the position of the seat back frame. 3.The vehicle seat according to claim 2, further comprising a seat cushionpad supported by the seat cushion frame, and provided with a recessedportion recessed forward from a part of a rear edge of the seat cushionframe corresponding to the curved portion, wherein the buckle supportarm is positioned in the recessed portion in such a manner that the seatcushion pad is positioned in the rotational locus of the buckle supportarm and the buckle when the seat cushion frame is positioned in therearmost position in correspondence to the position of the seat backframe, and out of the rotational locus of the buckle support arm and thebuckle when the seat cushion frame is positioned in a more forwardposition in correspondence to the position of the seat back frame. 4.The vehicle seat according to claim 3, wherein an upper end of thebuckle is lower than an upper surface of the seat cushion pad in thestowed position.
 5. The vehicle seat according to claim 1, furthercomprising a biasing device for urging the buckle support arm toward theuse position.
 6. The vehicle seat according to claim 1, furthercomprising a reinforcing member extending in the fore and aft directionbetween the curved portion and the front frame.
 7. The vehicle seataccording to claim 1, further comprising an intermediate frame extendinglaterally between the side frames intermediately between the front frameand the rear frame, and a reinforcing member extending in the fore andaft direction between the curved portion and the intermediate frame. 8.The vehicle seat according to claim 1, wherein the rear frame includes aleft portion and a right portion extending laterally on either side ofthe curved portion, and the seat cushion frame defines a pair of seatingparts, the left portion forming a rear part of one of the seating parts,the right portion forming a rear part of the other of the seating parts,and the curved portion is positioned at a boundary between the twoseating parts.
 9. The vehicle seat according to claim 8, wherein thecurved portion, the left portion, and the right portion are formed by acontinuous pipe member.
 10. The vehicle seat according to claim 8,wherein the left portion and the right portion are vertically offsetfrom each other.
 11. The vehicle seat according to claim 8, wherein theseat cushion frame forms two seating parts in a rear seating arrangementincluding a left seating part, a middle seating part, and a rightseating part that are arranged laterally, the two seating parts beingformed by one of the left and right seating parts, and the middleseating part, and one of the left portion and the right portioncorresponding to the left seating part or the right seating part isoffset downward relative to the other of the left portion and the rightportion corresponding to the middle seating part.
 12. The vehicle seataccording to claim 8, further comprising a rear frame reinforcing memberconnected to the left portion and the right portion, and curved and/orbent downward in a part thereof corresponding to the curved portion. 13.The vehicle seat according to claim 1, wherein the curved portion has aV shaped configuration projecting forward in plan view.